diff --git a/doc/configuration.txt b/doc/configuration.txt
index 6f6c1bc..1ce423b 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -12870,11 +12870,14 @@
   the presence of a certain key in a table tracking some elements (e.g. whether
   or not a source IP address or an Authorization header was already seen).
 
-ipmask(<mask>)
-  Apply a mask to an IPv4 address, and use the result for lookups and storage.
+ipmask(<mask4>, [<mask6>])
+  Apply a mask to an IP address, and use the result for lookups and storage.
   This can be used to make all hosts within a certain mask to share the same
-  table entries and as such use the same server. The mask can be passed in
-  dotted form (e.g. 255.255.255.0) or in CIDR form (e.g. 24).
+  table entries and as such use the same server. The mask4 can be passed in
+  dotted form (e.g. 255.255.255.0) or in CIDR form (e.g. 24). The mask6 can
+  be passed in quadruplet form (e.g. ffff:ffff::) or in CIDR form (e.g. 64).
+  If no mask6 is given IPv6 addresses will fail to convert for backwards
+  compatibility reasons.
 
 json([<input-code>])
   Escapes the input string and produces an ASCII output string ready to use as a
diff --git a/src/sample.c b/src/sample.c
index 8de076b..655e734 100644
--- a/src/sample.c
+++ b/src/sample.c
@@ -1603,11 +1603,28 @@
 	return 1;
 }
 
-/* takes the netmask in arg_p */
-static int sample_conv_ipmask(const struct arg *arg_p, struct sample *smp, void *private)
+/* takes the IPv4 mask in args[0] and an optional IPv6 mask in args[1] */
+static int sample_conv_ipmask(const struct arg *args, struct sample *smp, void *private)
 {
-	smp->data.u.ipv4.s_addr &= arg_p->data.ipv4.s_addr;
-	smp->data.type = SMP_T_IPV4;
+	/* Attempt to convert to IPv4 to apply the correct mask. */
+	c_ipv62ip(smp);
+
+	if (smp->data.type == SMP_T_IPV4) {
+		smp->data.u.ipv4.s_addr &= args[0].data.ipv4.s_addr;
+		smp->data.type = SMP_T_IPV4;
+	}
+	else if (smp->data.type == SMP_T_IPV6) {
+		/* IPv6 cannot be converted without an IPv6 mask. */
+		if (args[1].type != ARGT_IPV6)
+			return 0;
+
+		*(uint32_t*)&smp->data.u.ipv6.s6_addr[0]  &= *(uint32_t*)&args[1].data.ipv6.s6_addr[0];
+		*(uint32_t*)&smp->data.u.ipv6.s6_addr[4]  &= *(uint32_t*)&args[1].data.ipv6.s6_addr[4];
+		*(uint32_t*)&smp->data.u.ipv6.s6_addr[8]  &= *(uint32_t*)&args[1].data.ipv6.s6_addr[8];
+		*(uint32_t*)&smp->data.u.ipv6.s6_addr[12] &= *(uint32_t*)&args[1].data.ipv6.s6_addr[12];
+		smp->data.type = SMP_T_IPV6;
+	}
+
 	return 1;
 }
 
@@ -2809,7 +2826,7 @@
 	{ "length", sample_conv_length,    0,            NULL, SMP_T_STR,  SMP_T_SINT },
 	{ "hex",    sample_conv_bin2hex,   0,            NULL, SMP_T_BIN,  SMP_T_STR  },
 	{ "hex2i",  sample_conv_hex2int,   0,            NULL, SMP_T_STR,  SMP_T_SINT },
-	{ "ipmask", sample_conv_ipmask,    ARG1(1,MSK4), NULL, SMP_T_IPV4, SMP_T_IPV4 },
+	{ "ipmask", sample_conv_ipmask,    ARG2(1,MSK4,MSK6), NULL, SMP_T_ADDR, SMP_T_IPV4 },
 	{ "ltime",  sample_conv_ltime,     ARG2(1,STR,SINT), NULL, SMP_T_SINT, SMP_T_STR },
 	{ "utime",  sample_conv_utime,     ARG2(1,STR,SINT), NULL, SMP_T_SINT, SMP_T_STR },
 	{ "crc32",  sample_conv_crc32,     ARG1(0,SINT), NULL, SMP_T_BIN,  SMP_T_SINT  },